Method for operating a water circulation system

ABSTRACT

A method for operating a water circulation system having at least one valve and at least one temperature sensor; determining a first temperature and a second temperature; determining a period of time; detecting the water temperature using at least one temperature sensor; detecting the opening time during which the at least one valve is at least partially open at least partially opening the at least one valve if the detected water temperature exceeds the value of the first temperature or if the opening time reaches the period of time; and completely closing the at least one valve if the detected water temperature reaches the value of the second temperature.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a method for operating a water circulation system, in particular a piped drinking or service water system.

DESCRIPTION OF THE RELATED ART

Operating methods for water circulation systems are known from the prior art in which the water temperature must be kept above or below a predefined temperature in order not to promote the growth of germs. The growth of germs such as Pseudomonas aeruginosa or Legionella is particularly favored in a temperature range of 20 to 50° C. For reasons of hygiene, i.e. to prevent germ growth as much as possible, the water temperature should therefore not be kept in this range. For reasons of convenience, i.e. to be able to quickly achieve a sufficiently high mixed temperature, the hot water temperature is usually kept at 55° C. Since the hot water pipes cannot be perfectly insulated, heat is continuously given off from the pipes to the cooler environment; usually 8 to 10 watts per meter. The greater the temperature difference between the hot water and the environment, the greater the heat loss in the pipes. To keep the hot water temperature at 55° C., it has to be heated continuously, which means that energy is constantly required for heating. Accordingly, the cold water should be kept below 20° C. Since the cold water pipes cannot be perfectly insulated either, the pipes continuously absorb heat from the warmer environment. The greater the temperature difference between the cold water and the environment, the greater the heat absorption of the pipes. In order to keep the water temperature permanently below 20° C. in a cold water system, cooling must be carried out continuously, which means that energy is constantly required for cooling. Furthermore, with today's systems, the hydraulic balancing of the individual circuits must be carried out manually in accordance with the planner's information. If this adjustment is not carried out, which is often the case in practice, the valve of each strand is usually completely or almost completely open, which means that the greatest amount of water circulates in the strand with the shortest connection line to the temperature control unit. Accordingly, this strand is the warmest in a hot water circuit and the coolest in a cold water circuit. The strand with the longest connection line to the temperature control unit is accordingly the coolest in the hot water circuit and the warmest in the cold water circuit. In case of a circuit without hydraulic balancing of the individual strands, the required target temperature can no longer be achieved, which represents a high safety risk.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a method for operating a drinking or service water system which is more energy-efficient. The method is also intended to enable automatic hydraulic balancing of the strands of the drinking or service water system.

This object is achieved by a method with the features of claim 1. Further embodiments of the method are defined by the features of further claims.

A method for operating a water circulation system according to the invention comprises the steps of:

-   -   Providing the water circulation system, comprising:         -   at least one supply line,         -   at least one return line,         -   at least one strand (3) which connects the supply line (1)             with the return line,         -   at least one temperature control unit, which connects the             supply line with the return line,         -   whereby water can circulate in a flow direction from the at             least one supply line, via the at least one strand, the at             least one return line and the temperature control unit back             to the supply line,         -   at least one consumer, which is arranged along the at least             one line and with which water can be drawn from the             circulation system,         -   at least one valve with which the flow rate of the water in             the circulation system can be changed,         -   at least one temperature sensor with which the water             temperature can be detected in a line section,         -   at least one control unit with which the data from the             temperature sensors can be processed and with which the at             least one valve can be actuated;     -   Defining a first temperature;     -   Defining a second temperature;     -   Defining a time duration;     -   Detecting the water temperature with the at least one         temperature sensor;     -   Detecting the opening time during which the at least one valve         is at least partially open;     -   Opening the at least one valve at least partially when the         detected water temperature reaches the value of the first         temperature or when the opening time reaches the time duration;     -   Completely closing the at least one valve when the detected         water temperature reaches the value of the second temperature.

Such a method has the advantage that the heat losses can be kept lower, since the heat transfer from the water to the pipe is smaller when the water is still than when the water is flowing. In this way, the amount of heat flowing off into the environment can be reduced, so that less heat energy has to be supplied to the system, which makes the system more energy-efficient. Another advantage is that in a system with several strands, by completely closing the valve of one strand, more water can flow in the other strands. When the water in the first strand has reached the target temperature, the corresponding valve is completely closed, which means that more water is available to the other strands, so that they can reach the target temperature more quickly. With this method, an automatic hydraulic balancing of the individual strands is realized, whereby the target temperature can be reached safely and as quickly as possible in all stands. With these method steps it can be prevented, for example, that the water temperature at a location in the circuit can fall below the permissible value without this being recognizable. If the temperature sensor of a strand is located, for example, in a heating room, the water temperature measured by the sensor corresponds increasingly to the local ambient temperature of the sensor when the valve is completely closed. After installation, a fixed value can be set for the time duration of each strand and the value will not be changed afterwards.

A consumer can be any type of water extraction point, for example a sink, shower, bathtub or the like.

A valve can be any type of valve that can be opened and closed with an actuator, the actuator being controllable by the control unit.

A temperature sensor can be any type of temperature sensor with which the water temperature can be reliably measured in a range from 5 to 60° C. The temperature sensor can be in direct contact with the water to be measured or it can be separate from the water, i.e. it can be arranged on the outside of the corresponding line.

The control unit can be any type of control unit which enables temperatures to be defined, the temperatures detected by the temperature sensor to be compared with the defined temperatures and with which the valve can be controlled on the basis of the comparison, i.e. can be at least partially opened or closed.

For example, a first permissible temperature can be defined as the first temperature and a second permissible temperature can be defined as the second temperature. In a hot water system, the first temperature can be a lower permissible temperature and the second temperature can be a higher permissible temperature. For example, the upper temperature can be 56° C. and the lower temperature 55° C. In a cold water system, the first temperature can be an upper permissible temperature and the second temperature can be a lower permissible temperature. For example, the upper temperature can be 16° C. and the lower temperature 15° C.

In one embodiment, the method comprises the step of:

-   -   Recording the course of the recorded temperature.

By recording the temperature profile, not only the actual value but also the change in temperature over time can be determined.

In one embodiment, the method comprises the steps of:

-   -   Determining the gradient of the recorded temperature profile;     -   Changing the opening of the valve based on the determined         temperature gradient.

If the second temperature is to be reached as quickly as possible, the valve is opened to the maximum. If a less strong increase in temperature is desired, the valve is only partially opened.

In one embodiment, the method comprises the steps of:

-   -   Assigning the recorded temperature profile to a specific         consumption;     -   Changing the opening of the valve based on the specific         consumption.

For example, a temperature profile can be assigned to washing hands, showering or taking a bath. Washing hands uses a small amount of water over a short period of time. Taking a shower uses more water over a longer period of time, and taking a bath uses a lot of water over a long period of time. If water is withdrawn at a consumer, water flows from the supply line and from the return line in the direction of this consumer. I.e. the water at the temperature sensor arranged in the strand flows backwards at this moment, i.e. against the direction of flow. Since the backward-flowing water has lingered in the line for a long time and is cooler due to the constant loss of heat, a decrease in temperature can be determined on the temperature sensor during consumption. However, the assignment can only take place when the valve is at least partially open, since only then can the water flow in the corresponding strand against the general direction of flow.

In one embodiment, the method comprises the steps of:

-   -   Defining at least one trigger threshold;     -   Detecting a time interval during which the at least one trigger         threshold is exceeded;     -   Assigning a specific consumption to the recorded time interval.

The trigger threshold can be defined as a temperature value or as a temperature difference to the set temperature. The trigger threshold can also be the set temperature. Several different trigger thresholds can be defined.

In one embodiment, the method comprises the steps of:

-   -   Defining at least one time window;     -   Executing the method within the at least one time window;     -   Opening the at least one valve at least partially outside of the         at least one time window.

For example, a period of the day in which only low consumption is to be expected can be provided as the time window. Several time windows can also be distributed over the day. For example, the time windows can be provided between the main consumption times. Usually, the consumption in the morning, at noon and in the evening is higher than in the time in between. Outside of this time window, the valve can be partially or fully open to keep the temperature level high so that the user does not have to wait long for warm or cold water. Usually, the most water is used in the morning, at noon and in the evening.

Accordingly, the time windows can be set in the periods in between. For example, from midnight to 6 a.m., from 9 a.m. to 11 a.m., from 1 p.m. to 6 p.m. and from 8 p.m. to midnight.

In one embodiment, the method comprises the steps of:

-   -   Extending the time duration if the water temperature detected at         the beginning of the at least partial valve opening is above the         value of the first temperature;     -   Shortening the time duration if the water temperature detected         at the beginning of the at least partial valve opening is below         the value of the first temperature.

With these process steps, the time duration can be adapted to the currently prevailing conditions. The surroundings of the system are, for example, warmer during the day or in summer than at night or in winter. Accordingly, it makes sense to adjust the time periods accordingly.

In one embodiment, the at least one temperature sensor is arranged in the immediate vicinity of the at least one valve. For example, it can be arranged before, immediately before, after or immediately after the valve. Alternatively, the at least one temperature sensor is arranged in the at least one valve, i.e. the temperature sensor is integrated in the valve.

In one embodiment, the water circulation system comprises a temperature sensor on the supply line, in the area of the temperature control unit, with which the supply temperature can be detected. In this way, the temperature difference between the flow temperature and the temperature measured on the strand can be determined, whereby conclusions can be drawn about the heat loss in the supply part of the pipe system. Alternatively or additionally, the water circulation system comprises a temperature sensor in the area of the temperature control unit, with which the return temperature can be detected. Thus, the temperature difference between the strand temperature and the return temperature can be determined, whereby conclusions can be drawn about the heat loss in the return part of the pipe system. The principle is the same in a cold water system, but the heat absorption can be determined.

In one embodiment, the water circulation system comprises two or more strands, each with at least one consumer, at least one valve and at least one temperature sensor, each of the stands comprising its own control unit. In the case of an individual strand control, for example, the valves of all strands are fully open. As soon as the temperature sensor of one strand reaches the second temperature, the corresponding valve is closed, which means that warm water can reach the other strands more quickly. This reduces the heat loss in the strand with the standing water. As soon as the second temperature is measured in all strands, all valves are closed. The heat loss is reduced in all strands. Alternatively, all strand can comprise a common control unit. With a common control unit, for example, rocking effects can be suppressed, which makes the system more stable.

In one embodiment, the water circulation system comprises a pump, a non-return valve and a filter. The pump provides the necessary pressure increase to circulate the water in the system. The non-return valve, for example a check valve, prevents water from flowing back from the temperature control unit into the return line. Alternatively or additionally, a non-return valve can be provided in the supply line and prevent water from flowing back from the system into the public water connection. The filter cleans the water in the circulation system and can be used in the supply line before the temperature control unit or in the system, i.e. be provided in the supply line, the strand or the return line.

In one embodiment, the at least one temperature control unit comprises a heating unit or a cooling unit.

In one embodiment, the water circulation system comprises at least one hot water circulation system with a heating unit and a cold water circulation system with a cooling unit.

The mentioned embodiments of the method can be combined as desired, provided they do not contradict one another.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the current invention are described in more detail in the following with reference to the figures.

These are for illustrative purposes only and are not to be construed as limiting. It shows

FIG. 1 a schematic representation of a water circulation system for carrying out the method according to the invention;

FIG. 2 a schematic representation of a temperature profile in a strand of the water circulation system of FIG. 1;

FIG. 3 a schematic illustration of a further temperature profile in a strand of the water circulation system of FIG. 1; and

FIG. 4 a schematic illustration of a temperature profile in a strand of the system of FIG. 1 during specific consumptions.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a schematic representation of a water circulation system for carrying out the method according to the invention. The system comprises a supply line 1, a return line 2, two strand 3 which connect the supply line 1 to the return line 2. The system further comprises a temperature control unit 4, which connects the supply line 1 with the return line 2, whereby in one flow direction, water can circulate from the supply line 1, via the two strands 3, the return line 2 and the temperature control unit 4 back to the supply line 1. The system further comprises several consumers 5, which are arranged along the strand 3 and with which water can be drawn from the circulation system. In each strand 3, a valve 6 is provided, which is arranged in the region of the strand 3 which opens into the return line 2. I.e. the valve 6 is arranged in the region of the end of the strand 3. With each valve 6, the flow rate of the water in the respective strand can be changed. In the supply line 1, in the area of the temperature control unit 4, a temperature sensor 60 is provided with which the supply temperature T_(V) can be detected. A further temperature sensor 61 is provided in the strand 3 in the area of the valve 6, with which the strand temperature T_(S) can be detected. In the return line 2, in the area of the temperature control unit 4, a further temperature sensor 62 is provided, with which the return temperature T_(R) can be detected. The system further comprises a strand-specific or an overall control unit (not shown) with which the data from the temperature sensors can be processed and with which the at least one valve can be actuated. A circulation pump 7 is provided in the return line 2, with which water can be conveyed from the strands 3 via the return line 2 to the temperature control unit 4. A check valve 8 is provided between the pump 7 and the temperature control unit 4, which prevents water from flowing back from the temperature control unit 4 to the pump 7. A public supply line leads from the public water connection to the temperature control unit 4. A filter 9 is provided in the public supply line, which can clean the tap water from the public connection. A check valve 8 is provided between the filter 9 and the public connection, which prevents water from flowing back from the temperature control unit 4 to the public connection.

FIG. 2 shows a schematic diagram of a temperature profile in a strand 3 of the water circulation system of FIG. 1.

In a hot water system, the tap water circulates in the first intervals I₁ and the water stands still in the second intervals I₂. The strand temperature T_(S) is kept between the first temperature T₁ and the second temperature T₂. If the temperature sensor of the strand indicates that the measured water has the first temperature T₁, the valve 6 is opened at least partially, as a result of which the water temperature in the strand 3 rises. When the strand temperature T_(S) reaches the second temperature T₂, the valve 6 is closed. When the valve 6 is closed, the strand temperature T_(S) decreases over time. If it reaches the first temperature T₁, the valve is opened again. The more the valve is opened, the faster the second temperature is reached and the shorter the heating interval.

In a cold water system, the tap water circulates in the second intervals I₂ and the water stands still in the first intervals I₁. As soon as the circulation starts, the strand temperature T_(S) decreases and as soon as the water stands still in the strands, the temperature of the strand water increases.

FIG. 3 shows a schematic representation of a further temperature profile in a strand 3 of the water circulation system of FIG. 1. In the temperature profile shown, the valve 6 is at least partially open in the first section, as a result of which the temperature T_(S) measured in the strand increases. If the predefined second temperature T₂ is reached, the valve 6 is completely closed. The valve is kept closed for a first period of time Z_(D1), as a result of which the measured strand temperature T_(S) decreases over time. After the first time period Z_(D1) has elapsed, the valve is opened again and the water temperature of the strand is determined. If the determined temperature is higher than the predefined first temperature T₁, then the second time period Z_(D2) following the first time period Z_(D1) is extended. This is repeated until the period is such that when the valve is opened, the strand temperature corresponds to the first temperature. If, after opening the valve, a water temperature is determined which is lower than the first temperature, the next time period is shortened.

FIG. 4 shows a schematic representation of a temperature profile in a strand of the system of FIG. 1 during specific consumption levels V₁,V₂,V₃. If the strand temperature T_(S) changes only slightly during a short interval I₁, then this can be assigned to hand washing V₁. A larger change in temperature over a longer interval I₂ can be assigned to a shower V₂ and a large change in the strand temperature over a long interval I₃ can be assigned to filling up a bathtub V₃. In a further alternative, the time is taken into account at which the measured temperature in a hot water system falls below a predetermined temperature or exceeds it in a cold water system. Such a trigger or release threshold can be set in such a way that, for example, minor temperature fluctuations are ignored and the time of the temperature drop is only taken into account when the trigger threshold is exceeded. The trigger threshold can be 0.1° C., 0.2° C., 0.4° C., 0.5° C., 1° C., 1.5° C., 2° C., 2.5° C., 3° C. or more. The trigger threshold can also be used to identify specific consumptions. The time during which the trigger threshold is exceeded is measured. Very short times, i.e. times of less than 5 seconds can be ignored. With a time of 5 to 15 seconds, it can be concluded that someone was washing their hands at a sink, for example. With a time of 30 seconds to 15 minutes, for example, a shower can be recognized and with a time of 10 to 30 minutes the taking of a bath can be recognized. The recording of the temperature profile can be designed in such a way that it only takes place when the measured temperature in the strand exceeds the trigger threshold, i.e. the deviation from the set temperature exceeds a certain value. Alternatively, as described above, the time during which the trigger threshold is exceeded can be measured to determine a specific consumption V₁,V₂,V₃. The time interval during which the trigger threshold is exceeded can therefore be used to identify the specific consumption. A very short interval can be ignored. A short interval indicates hand washing, a longer interval indicates showering and a long interval indicates taking a bath.

Several trigger thresholds can also be defined so that the determination is not based solely on time, i.e. based on the length of the intervals. In this way, it can be determined during which time which trigger threshold is exceeded. If only the first trigger threshold is exceeded, this indicates hand washing. If the first trigger threshold is exceeded during a first interval and a second trigger threshold is exceeded during a second interval, the first trigger threshold being smaller than the second and the first interval being longer than the second, this indicates showering. Any number of trigger thresholds and intervals can be combined with one another and compared for an evaluation. The preset strand temperature can also be used as the trigger threshold.

REFERENCE SIGNS LIST 1 Supply line I_(1,2,3) Interval 2 Return line T_(V) Supply temperature 3 Strand T_(S) Strand temperature 4 Temperature control T_(R) Return temperature unit T₁ First temperature 5 Consumer T₂ Second temperature 6 Valve V_(1,2,3) Consumption 60 Temperature sensor Z_(D) Time duration 61 Temperature sensor Z_(F) Time window 62 Temperature sensor 7 Pump 8 Non-return valve 9 Filter 

1. A method for operating a water circulation system comprising the steps of: providing the water circulation system, comprising: at least one supply line (1), at least one return line (2), at least one strand (3) which connects the supply line (1) with the return line (2), at least one temperature control unit (4), which connects the supply line (1) with the return line (2), whereby water can circulate in a flow direction from the at least one supply line (1), via the at least one strand (3), the at least one return line (2) and the temperature control unit (4) back to the supply line (1), at least one consumer (5), which is arranged along the at least one line (3) and with which water can be drawn from the circulation system, at least one valve (6) with which the flow rate of the water in the circulation system can be changed, at least one temperature sensor (60,61,62) with which the water temperature can be detected in a line section, at least one control unit with which the data from the temperature sensors (60, 61, 62) can be processed and with which the at least one valve (6) can be actuated; defining a first temperature (T₁); defining a second temperature (T₂); defining a time duration (Z_(D)); detecting the water temperature with the at least one temperature sensor (60,61,62); detecting the opening time during which the at least one valve (6) is at least partially open; opening the at least one valve (6) at least partially when the detected water temperature reaches the value of the first temperature (T₁) or when the opening time reaches the time duration (Z_(D)); completely closing the at least one valve (6) when the detected water temperature reaches the value of the second temperature (T₂).
 2. The method according to claim 1, comprising the step of: recording the course of the recorded temperature.
 3. The method according to claim 2, comprising the steps of: determining the gradient of the recorded temperature profile; changing the opening of the valve (6) based on the determined temperature gradient.
 4. The method according to claim 2, comprising the steps of: assigning the recorded temperature profile to a specific consumption (V_(1,2,3)); changing the opening of the valve (6) based on the specific consumption.
 5. The method according to claim 2, comprising the steps of: defining at least one trigger threshold; detecting a time interval (I_(1,2,3)) during which the at least one trigger threshold is exceeded; assigning a specific consumption (V_(1,2,3)) to the recorded time interval (I_(1,2,3)).
 6. The method according to claim 1, comprising the steps of: defining at least one time window (Z_(F)); executing the method within the at least one time window (Z_(F)); opening the at least one valve (6) at least partially outside of the at least one time window (Z_(F)).
 7. The method according to claim 1, comprising the steps of: extending the time duration (Z_(D)) if the water temperature detected at the beginning of the at least partial valve opening is above the value of the first temperature (T₁); shortening the time duration (ZD) if the water temperature detected at the beginning of the at least partial valve opening is below the value of the first temperature (T₁).
 8. The method according to claim 1, wherein the at least one temperature sensor (61) is arranged in the immediate vicinity of the at least one valve (6) or wherein the at least one temperature sensor (61) is arranged in the at least one valve (6).
 9. The method according to claim 1, wherein the water circulation system comprises a temperature sensor (60) on the supply line (1) in the area of the temperature control unit (4), with which the supply temperature (T_(V)) can be detected and/or wherein the water circulation system comprises a temperature sensor (62) in the area of the temperature control unit (4) with which the return temperature (T_(R)) can be detected.
 10. The method according to claim 1, wherein the water circulation system comprises two or more strands (3) each with at least one consumer (5), at least one valve (6) and at least one temperature sensor (60,61,62), wherein each of the strands (3) comprises its own control unit or wherein all strands (3) comprise a common control unit.
 11. The method according to claim 1, wherein the water circulation system comprises a pump (7), a non-return valve (8) and a filter (9).
 12. The method according to claim 1, wherein the at least one temperature control unit (4) comprises a heating unit or a cooling unit.
 13. The method according to claim 11, wherein the water circulation system comprises at least one hot water circulation system with a heating unit and a cold water circulation system with a cooling unit. 